rockstroh



Jan. 30, 1923. 1,443,433.

I O. ROCKSTROH.

ROLL FILM DARK SLIDE.

FILED AUG. 8. I921. 2 SHEETS-SHEET 1.

Jan. 30, 1923. 1.443, 133.

0. ROCKSTROH.

ROLL FILM DARK SLIDE. Y men AUG.8, 1921.

2 SHEETS-SHEET Z- 7 roll fi tized film surface.

- and the plane Slate the film can be Patented Jan. 30, 1923.

UNITED STATES PATENT OFFICE.

OTTO BOCKSTROH, OF JENA, GERMANY, ASSIGNOR TO THE m 01' Cm ZEISS, OI JENA, GER-MANY.

noLL-m mm: s nner.

Application fled-August 8, 1981. Serial Io. 490,720.,

'To all who mit may cmwe'm:

Be it known that I, O'rro Rooxs'raon, a,

citizen of the German Empire; residing at Jena, Germany, have invented a new and useful Roll-Film Dark Slide, of which the following is a specification.

fiat form, this curling becoming all the more evident, the greater the part of the film to be ex .sed.

For avoiding this drawback dark slides for larger sizes have therefore been provided with 'a device inwhichjthe part of the film to be exposed is pressed from the back against a plane-parallel glass plate by means of a plane plate. However, the insertion of such a glass plate into the path of the rays of light is accompanied by a number of drawbacks. For instance, the rays of light are partly reflected ;at the limiting surfaces of the .plate, which not only invo es a loss oflight, but which may also giverise to interference fringes.

Further disadvantages of the glass plate are for instance, that it is apt to become soiled, and that it may cause scratches on the sensi- According to thejinvention the curling of the film may be avoided without introduc- -ing a glassplate into the path of the rays,

and the drawbacks involved by this plate be therefore avoided, by providing the dark slides with a device by means of which the part of the film to be exposed may be sucked from the back onto a plane plate. For sucking out the air between the film and the plane plate the plate is suitablyprovided with a number of channels, which are in connection with an air-pump consisting, for instance, of a cylinder and, movable in it, a

piston, or of extendible bellows. If a particularl good rarefaction of the air,'lasting for as ong a time as possible, is to be secured, the disposal of a frame corres onding' .in size to. the ima s to be produce on the film is recommen ed, betweenwhich' frame rexe'd,

so that a close upspace is formed tween the film and plate. In, order obtain the desired rarefaction of the air at as slight a movement as possible of the member to be displaced forf-sucking the air out of the space between the film and the plane plate, hence, e.- g., of the said piston, or of the hood to be guided loosely of the said bellows, the frame would, of course, have to be pressed against the fihn, beforethe suction commences (e. g., by means of cam discs or by .a lever device). However, at the beginning of the suction wrinkles will frequently be formed in the film which would then have no chance of escapin from the space enclosed'by the frame.

11 consideration of this fact a controlling device is suitably fitted, by means of which the pressing movement of the frame is made dependent on the movement of the member to be displaced-for sucking the air out of the space between the film and the plane plate.

The possibility is then given, by appropriately setting the controlling device, to

have the frame pressed against the film but a certain time after the beginning of the suction, during space of time any wrinkles which might be formed may escape fromthe space enclosed by the frame. It will furthermore serve for the removal of such wrinkles to so choose'the contrivance for suckin the film onto the plane plate that from t e beginning the film is more effectively sucked on in the middle of the plane plate than towards the margin, which may, e. g., be attained by connecting the channels in the plate with the air-pump in successive order, that is to say, those in the middle of the platebefore those existing towards the margin, or, when all the channels in the plane plate are permanently in connection with the airump, by, giving the channels in' the middle of the plate a larger transverse section than those situated towards the margin: In order to be able to maintain a certain degree of rarefaction of the air between the film and the plane plate automatically, should air subsequently enter between the film and the plate, it will be found convenient to have springs disposed placed for 'sucking the air out,.in which for the movement of the member to be dis- 1 manner the said member is constantly kept I under tension even after the suction, and it is automatically kept moving when air enters. I

In the annexed drawing: Figs. 1 to '4 show a" constructional example of a dark slide equipped according to the present invention, Fig. 1 being a side elevation of the dark slide, Fig. 2 a section through it along the line 22 of Fig. 3, Fig. 3 a back view of the dark slide, with the rear shutter partly withdrawn, and :Fig. 4 a view of the plane plate onto which the film is to be sucked.

'In the casing m of the dark slide which may be closed by means of two shutters a and i a the former of which faces the camera, two film spools, a supply spool b and a receiving spool 6 are removably fitted. Opposite the opening which may be closed by means of the shutter a there is fixed to the casing by means of angle plates c a plane plate 0, which is provided with channels 0 c and c and, at the surface turned towards the dark slide opening, with grooves 0 The transverse sections of the channels are so chosen as to differ in size, the channels 0 having the smallest and the channels 0 a medium transverse section whilst the channel 0 in themiddle of the late shows the largest transverse section. ith theplate c an extendible bellows d is connected, which are closed by a back plate (13 guided loosely in grooves 65. Springs 6, which are fastened, on the one hand, to the back plate and, on the other hand, to the casing of the dark slide, impart to the said back plate the tendency, to assume a position in which the bellows is extended. When the back plate d has been brought into the opposite position, againstthe tension of the springs 6, it is held in this position 'by means of spring operated pawls-e". Between the plane plate a and the dark slide wall to be turned towards the camera a frame f is so disposed that it may be displaced per endicularly to the plate 0 between guidears 7, which,

are fixed to the dark slide casing. Between the frame and the plane plate the film, marked b, is passed, so thatit ma be ressed against the plate by means 0 the rame. In order to have the connection .between the film and the plate as air-tight as posslble, the frame as well as the plate are padded with felt-strips g.- Four springs f a A (df which only two may be seen in, the a drawing), which are fixed to the dark slide casing, serve for pressing the frame 7 onto the plate 0, while two spring-operated pawls f serve for keeping the frame against the tension of the springs f in a position in which its distance from the plate 0 is. suth that the. film may be freely "passed between it and the plate. Furthermore,.between the back plate-at and either of the two pawls f a controlhng device isv disposed, each of which consists of a set-screw h a cranked lever 71, a two-armed lever. h. ,,and a projection 72, fixed to the ,back plate J Besides, to each of the pedestal bodies for the two-arined levers a plate-spring k is fixed,

of the side-walls of the dark slide a crank i is? fitted, the shaft of which is coupled with the spool 12 by means of a pair of toothed wheels 7?, 2' and, in addition, is connected with a shaft 70 by a belt-drive. The shaft of the toothed wheel 2' is, likewise by a belt-,drive, coupled with another sha'ft Z. The ratio of the diameters of the pitch circles of the two toothed wheels is so chosen that the respective diameter of the wheel z" amounts to four'units, when the corre sponding diameter of the wheel i is assumed to have three units. A quarter of the number of teeth of the wheel a? has,

however, been cut away, so that, during one revolutlon of the crank i the wheel 7, also makes one revolution only, the arrangement being made in'such' a,manner that, on the crank being rotated from the zero-position, which is made known by anotch i during one quarter revolution the wheel 11 takles no part in the rotation. Furthermore, diameter of the driving wheel of the beltdrive actuating the shaft 70 is as big again as the diameter'of the driven wheel. The

diameters of the wheels of the belt-drive for actuating the shaft l are equal in size. To the shaft is two non-circular discs 7: are fixed which, on the shaft being rotated,

serve for pushing the frame f against the tension of the springs f into that position in which it is held by the pawls f whilst to the shaft Z two cranks Z are fixed,

which, on being rotated, are to displace thev back plate at of the bellows against the tension of the springs 0 until it becomes arrested by the pawls e- On that side of the dark slide to which the crank 11 is fixed there is, moreover, a two-armed lever m disposed, which is rotatable about an axis m, and one end of which is connected with one of the two pawls e by means of a cord m and with the other one of these pawls by means of a cord m passing over the rollers m m and by means of acord m, the other end being in contact with a knob m so that the pressing down of this knob causes a movement of the spring operated pawls e which is oppositely directed to their springtension. I .One exposure bring afresh portion of the film in the being made, in order to present dark slide into position fora further exposure, first of all the crank i is turned round once, and thereupon the knob m pressed down. By turning round the crank, in the first place, during the first quarterrevolution the shaft 70 is caused to make one is held by means of the pawls e;

I are by means of the cords m as half revolution. Thereby the frame f, which after the exposure was pressed against the film, is pushed by means of the curved discs 70 into the drawn position, in which it is held by the pawls f so that now the film may be freely passed between the plate 0 and the frame f. During the remaining part of the revolution of the crank the toothed wheel 2' is then caused to make one complete revolution, and the shaft It a further one and a half revolution, the shaft k running idle. The revolution of the toothed wheel causes in the first instance a revolution of the film spoolb and by this means a moving on of the film, and, besides, a complete revolution of the shaft Z and along with it of the cranks Z whereby the latter push the back plate Z of the bellows d, which was extended after the preceding exposure, into the drawn position, in which it By pressing'down the knob m the spring-pawlse well as m and m so far pulled back that the back plate d of the bellows is released and follows the influence of the springs e. In this manner the air in the bellows and in the space between the film and the plate a, which space is connected with the bellows by means: of the channels 0 c and 0*, becomes rarefied,

and the film is therefore sucked onto the plate, the frame f )at first still being held in the drawn position by means of the pawls f On the backlplate d then having covered part of its way, the projections h strike against the levers k by Which means the pawls f are moved against the tension of their springs, and thereby release the frame f, which may now follow the influence of the springs f ,-under which it is pressed against the film and the plate 0, whereby an as air-tight as possible connection between the film and the plate is ensured. The back plate of the bellows moves under the influence of the springs c until the air has been rarefied .to a certain degree, without, however, coming into contact with a stop yet; it, therefore, remains still further under the influence of the s rings, in .which manner the maintenance 0 a certain degree of rarefaction of the" air is continually aimed at.

I claim 1. In a roll film dark slide, a plane plate, and a device for sucking the portion of the film to be exposed from the back onto the said plate, this device being fitted in the interior of the dark slide.

2; In a roll film dark slide, a lane late, means for sucking the portion 0 the fi m to be exposed from the back onto the said plate, a frame corresponding to size of picture, and means for moving the said frame and the plane plate relatively to one another for pressing the film between the frame and the late. p 3. In a roll film dark slide, a plane plate, means comprising a member to be displaced for sucking the portion of the'film to be exposed from the back onto the said plate, a frame corresponding to size of picture,

means for moving the said frame and the plane plate relatively to one another for pressingthe film between the frame and the ,plate, and a controlling device adapted to make the relative movement of the frame and the plate dependent on the movement of'the said member.

4; "In a'roll film dark slide, a plane plate, means for sucking the portion of the film to be exposed from the back onto the said plate, and means for making-this suction at the ,beginnin more effective in the middle of the plate t an towards the mar 'n. OTTO ROCKS OH. Witnesses:

PAUL KRUGER, RICHARD HAHN. 

